The difference between Obj.field and Obj[field]

Obj is an object, and if one of its property names is field, the use of Obj.field can be accessed successfully, while using Obj[field] will cause an error because the contents in brackets are parsed into variables because the field variable is not defined and an error is made. So you can use obj[' field ' to access the variable

If field is a variable, then to dynamically access the properties of obj, only use Obj[field], you cannot use Obj.field, otherwise it will error

The difference between Obj.field and Obj[field]